To opt back into the warnings, add the following to the .analysis_options file for your project.

analyzer:
errors:
strong_mode_down_cast_composite: warning

Core libraries

dart:core

Added Uri.isScheme function to check the scheme of a URI. Example: uri.isScheme(“http”). Ignores case when comparing.

Make UriData.parse validate its input better. If the data is base-64 encoded, the data is normalized wrt. alphabet and padding, and it contains invalid base-64 data, parsing fails. Also normalizes non-base-64 data.

If in a Bazel workspace, then use the analysis options in package:dart.analysis_options/default.yaml if it exists.
Use the default analysis options rules.

In addition, specific to dartanalyzer:

an analysis options file can be specified on the command line via –options and that file will be used instead of searching for an analysis options file.

any analysis option specified on the command line (e.g. –strong or –no-strong) takes precedence over any corresponding value specified in the analysis options file.

Dartium, dart2js, and DDC

Imports to dart:io are allowed, but the imported library is not supported and will likely fail on most APIs at runtime. This change was made as a stopgap measure to make it easier to write libraries that share code between platforms (like package http). This might change again when configuration specific imports are supported.

Pub

Now sends telemetry data to pub.dartlang.org to allow better understanding of why a particular package is being accessed.

pub publish

Warns if a package imports a package that’s not a dependency from within lib/ or bin/, or a package that’s not a dev dependency from within benchmark/, example/, test/ or tool/.

No longer produces “UID too large” errors on OS X. All packages are now uploaded with the user and group names set to “pub”.

No longer fails with a stack overflow when uploading a package that uses Git submodules.

pub get and pub upgrade

Produce more informative error messages if they’re run directly in a package that uses Flutter.

Properly unlock SDK and path dependencies if they have a new version that’s also valid according to the user’s pubspec.

dartfmt

Support new generic function typedef syntax.

Make the precedence of cascades more visible.

Fix a couple of places where spurious newlines were inserted.

Correctly report unchanged formatting when reading from stdin.

Ensure space between – and —. Code that does this is pathological, but it technically meant dartfmt could change the semantics of the code.